Method of providing lower gloss protective covering for pre-press color proof

ABSTRACT

Method of providing an image-bearing surface, e.g., a pre-press proof, with a protective covering, comprising laminating to said surface a thin, substantially transparent integral polymeric film, the improvement wherein the polymeric film consists essentially of a mixture of at least two slightly incompatible polymers, whereby the film exhibits a 20° specular gloss that is at least 5% lower than the gloss of a film prepared from any one of said polymer constituents.

This application is a continuation of application Ser. No. 07/031,613filed 3/30/87 now abandoned.

FIELD OF THE INVENTION

This invention relates to a protective covering for imaged surfaceshaving a predetermined level of gloss. More particularly, it relates toa protective polymeric overcoat layer for an image-bearing surfacehaving a controlled level of lower gloss.

BACKGROUND OF THE INVENTION

In preparing an image-bearing photosensitive surface, such as apre-press proof or a photograph, it is frequently desirable to provide aprotective covering to prevent or limit scratching, marring, or otherdamage to the image-bearing surface. Such a covering must be opticallyclear so as not to obscure or distort the image. It should also haveflexibility, durability, and good adhesion to the image-bearingphotosensitive element.

Items or objects that people use or see in their daily lives range inappearance from high gloss to dull or flat. Highly glossy surfacesreflect a high proportion of the light directed at them specularly.Gloss can be defined as the degree to which the finish of a surfaceapproaches a perfect mirror. The closer the surface comes toapproximating the front surface of a mirror, the higher the gloss. Glosscan be measured at many different angles, but the gloss of the surfaceincreases with increasing angle of incidence from a line drawnperpendicular to the surface. Small angles of incidence, e.g., 20°,serve better to distinguish between examples exhibiting high gloss andare a better indication of gloss as perceived by the human eye. Inmeasuring specular gloss, those skilled in the art use higher anglemethods, e.g., 85°, to distinguish between lower gloss specimens and lowangle methods, e.g., 20°, to distinguish between high gloss samples. Ingeneral, the polymeric films described in this patent fall into the highgloss category and the most meaningful measure of gloss is, therefore,the gloss measurement at 20°.

Since gloss significantly affects the appearance of an image, one of themost important requirements for an overcoat or protective covering foran image-bearing surface is the ability to achieve the desired degree ofgloss. In many instances, it is desirable to modify the lightreflectivity of a photograph or other imaged surface to reduce highgloss. In the photoimaging and image reproduction industry, it isdesirable to modify the light reflectivity of the photosensitivematerials which are used to prepare pre-press color proofs, and, moreparticularly, to be able to match the gloss of the finished proof tothat of the ultimate pressprinted product. High gloss protectivecoverings or coversheets on pre-press multilayer color proofs, which aredesigned to permit evaluation of color rendition before the actualprinting run, interfere with the accurate assessment of color fidelitythroughout the lithographic tone scale. This result is generallyunacceptable to critical users of pre-press proofing methods.

The exact amount of gloss desired on a pre-press proof will varydepending on the type of end product whose appearance is to beduplicated, but in general, a level of 50-70 gloss units (as measured bya Gardner gloss meter at 20 degrees) is suitable for the commercialmarket in which the end product is a poster, brochure, or other printwhich is made on white, bright stock. On the other hand, there is apotential for great variability in the paper or other printing stockused in this segment of the industry and it may sometimes be necessaryto obtain much lower gloss levels, e.g., a 20° specular gloss lower than25, when highly matte printing stock is to be used. Prints made for thecommercial market are generally printed with a sheet-fed press toindividual, custom standards, which are not usually applicable to theentire industry. The ability to vary the degree of gloss on a pre-pressproof aimed at this segment of the industry is frequently of greatimportance, and the instant invention is particularly useful for thatpurpose.

Lower gloss prints suitable for the publication market, in which the endproduct is a magazine print, are generally made on a more yellow, darkerprinting stock. The actual printing is frequently performed on a webpress and the gloss is generally much lower, e.g., less than about 25gloss units. In addition, the print may have a matte appearance to lowerthe gloss and provide contrast for easier reading of the periodical. Inthese cases, the determination of specular gloss may best be performedat a grazing angle, (e.g., 85 degrees) to better distinguish betweenlower gloss specimens.

Photosensitive materials used in color proofing area of the positive- ornegative-working types. A positive-working process is described in U.S.Pat. No. 3,649,268 to Chu and Cohen. Positive-working materials maycontain tacky, photohardenable compositions which, when exposedimagewise to actinic radiation, harden in the exposed image areas,resulting in tacky and complementary nontacky image areas. The image canbe developed by applying colored particulate materials such as toners orpigments which selectively adhere to the unexposed tacky image areas.

A negative-working process is described in U.S. Pat. No. 4,174,216 toCohen and Fan, which teaches a negative-working element having asupport; a tacky, nonphotosensitive contiguous layer; a photohardenablephotoadherent layer; and a strippable coversheet. After imagewiseexposure to actinic radiation, the coversheet is peeled away, carryingwith it the exposed areas of the photoadherent layer, and baring thetacky continuous layer beneath. These areas of the tacky contiguouslayer lying underneath the exposed image areas may then be toned with afinely divided particulate material. Different colored layers can beprepared and assembled in register over one another to form multilayercolor proofs, as is well known to those skilled in the art. U.S. Pat.No. 4,053,313 to Fan describes a similar negative-working system whichis developed by solvent washout.

Alternatively, a photosensitive imaging system may be precolored withdyes and/or pigments or other coloring materials, developed by washout,contain photoplasticizing agents instead of photohardening agents, andother variations known to those skilled in the art. Negative-workingsystems may be achieved in a number of different ways, for example, byutilizing a photosensitive layer which becomes tacky and tonable onexposure to actinic radiation. It is understood that in addition tovarious photopolymer elements, other nonsilver halide systems, e.g.,diazo systems, are useful in preparing multicolor proofs. In addition,the described protective polymer layers of this invention may bebeneficially applied to many types of image bearing surfaces, e.g., aconventional silver halide photograph, where it is desired to provide aclear protective covering having a predetermined level of gloss. It isunderstood that the polymeric layers of the invention may also beapplied to nonimaged glossy surfaces to obtain a desired level oflowered gloss.

Photosensitive elements have been provided with a great variety ofprotective coverings. U.S. Pat. No. 4,077,830 to Fulwiler (1978) teachesthat photographic elements such as positives of negatives used forcontact printing can be protected by application of a thin transparentsheet of resin material having a thin coating of a transparentpressure-sensitive adhesive. To avoid image distortion during printing,both the resin sheet and the adhesive layer must be extremely smooth.The protective resin sheet is preferably Mylar®, a high glosspolyethylene terephthalate film manufactured by E. I. du Pont de Nemoursand Company, Wilmington, DE.

Stone, U.S. Pat. No. 3,397,980 (1968) relates to a protective laminatecomprising a durable outer layer such as Type D Mylar® and apolyethylene inner layer, bonded to microfilm using a polyvinyl acetatecoating. Type D Mylar® is very smooth and glossy.

Pre-press color proofs such as those described above are usually coveredwith one of three types of protective coverings or coversheets. Thefirst of these is a positive-working photosensitive element as describedin Chu and Cohen above, comprising a photosensitive layer and apolyester coversheet. This is exposed overall to actinic radiation andthe polyester coversheet removed. This results in a proof with adesirable 20° gloss level of about 65 gloss units. It suffers, however,from poor durability and is susceptible to crazing, scratching, andmarring.

The second type of topcoat or coversheet is a negative-workingphotosensitive element as described in Cohen and Fan, above, whichcomprises a polyester coversheet; a photosensitive layer; and an organiccontiguous layer. This is laminated to the proof and exposed overallwith the polyester coversheet left in place. The result is a proof witha more durable finish, but the gloss associated with the reflective,highly transparent integral polyester coversheet is unacceptably high,i.e., about 107 gloss units measured at 20 . The unacceptability of suchhigh gloss has long been recognized, and considerable effort has focusedon ways to achieve a durable lower gloss protective coating that isresistant to crazing, scratching, marring, etc.

The third type of protective covering or coversheet is an integral layerof plastic film, such as polyester, coated with a nonphotoactiveadhesive, and applied to the proof by lamination. The net result isindistinguishable from the second type of coversheet described above, inthat it provides a durable covering, but one which exhibits unacceptablyhigh gloss. For example, U.S. Pat. No. 4,329,420 to Bopp (1982) teachesa process of protecting pre-press proofs by applying a hard clearpolymer layer by means of a pressure-sensitive adhesive. Bopp utilizessuch high gloss materials as Mylar® polyethylene terephthalate.

A number of patents, however, teach methods of achieving a lower glossprotective coating for imaged surfaces. Many patents teach how toachieve coatings having a physically roughened or "matte" surface whichdiffuses light and has lowered gloss. For example, Spechler, U.S. Pat.No. 4,376,159 (1982), coats a transparent film-forming polymer on amatte-textured carrier sheet. The polymer is adhered to the surface of acolor-proofing surprint with a pressure sensitive adhesive. The carriersheet is then removed, leaving a matte-surfaced protective polymercoating on the surface of the proof.

King, U.S. Pat. No. 3,697,277 (1972) teaches a process for permanentlybonding a protective coating to a photographic print. A matte-surfacepolyester film is placed on the wet emulsion surface of a photographicprint and heat treated to permanently bond the film to the surface ofthe photograph.

Cohen and Fan, U.S. Pat. No. 4,286,046, recognizes the problemsassociated with the high gloss of a polyethylene terephthalate coveringand teaches a method for delustering a photopolymer pre-press proof byapplying particulate material to the tacky tonable layer.

A number of patents teach the use on photosensitive surfaces of mattelayers, comprising a resin having dispersed therein insoluble particlesor grains which impart a physical roughness to the surface. For example,U.S. Pat. Nos. 4,168,979 to Okishi et al., and 4,238,560, to Nakamura etal., teach a light sensitive printing plate with a matte overlayer,which is a resin layer with an insoluble particulate matting agentdispersed therein. This achieves a surface coarseness or roughness whichcontributes to improved exposure by the vacuum contacting method. Afterexposure the matte overlayer is removed with the developer. Similarly,U.S. Pat. No. 4,235,959, to This, deceased, et al., teaches aphotosensitive silver halide layer incorporating a layer comprisinggelatin and dispersed spherical particles which are the polycondensationproduct of urea, formaldehyde, and silica particles.

Although compatibility and incompatibility of polymers are recognizedphenomena, the prior art does not disclose integral films prepared fromblends of slightly incompatible polymers, nor does it teach how suchfilms can be laminated to imaged surfaces to provide a controlled degreeof lowered gloss. On the contrary, in general the prior art teaches thatincompatibility is undesirable and to be avoided.

U.S. Pat. No. 3,671,236, to Van Beusekom, teaches that in preparing aproof by superimposing a plurality of colored sheets, the individualsheets must be perfectly colorless and optically transparent in order toavoid any "haze" or imperfection being multiplied in the several sheets.

U.S. Pat. No. 4,323,636 to Chen teaches that in order to obtain atransparent, i.e., nonlight-scattering, photosensitive composition forpreparing printing plates, the binder and the monomer must becompatible. Incompatibility is evidenced by the formation of haze in thephotosensitive composition. By compatibility is meant the ability of theconstituents to remain dispersed with one another without causingappreciable scattering of light. This occurs when the monomer is solublein either of the component blocks of the block copolymer. Chen teachesonly how to avoid incompatibility of polymer and monomer inphotopolymerizable compositions. It does not deal withcompatibility/incompatibility of blends of polymers, nor does it suggestany utility for such incompatibility.

Gallagher et al., U.S. Pat. No. 3,811,924 (1974) teaches that an aqueouslacquer coating composition which is a blend of polymers consistingessentially of an ammonium salt of a copolymer of ethyl methacrylate andmethacrylic acid together with poly(vinyl acetate) can be applied toglossy surfaces to provide a degree of roughness or "matte". Gallagheralso teaches, however, that otherwise similar non-ammonium polymermixtures laid down from an organic solvent system would lack thedesirable matte finish. The polymeric films of the invention are notammonium salts, and they are coated on a substrate from an essentiallyorganic solvent system to form a smooth, low gloss integral film priorto laminating to the image-bearing surface.

BRIEF SUMMARY OF THE INVENTION

The invention relates to a protective covering for laminating to animage-bearing surface, comprising a thin, substantially transparent,integral polymeric film, the improvement wherein said polymeric filmconsists essentially of a mixture of at least two slightly incompatiblepolymers, whereby said film exhibits a 20° specular gloss that is atleast 5% lower than the gloss of a film prepared from any one of saidpolymer constituents.

The invention relates further to a method of providing an image-bearingsurface with a protective covering, comprising laminating to theimage-bearing surface a thin, substantially transparent integralpolymeric film, the improvement wherein the polymeric film consistsessentially of a blend of at least two slightly incompatible polymers,whereby said film exhibits a 20° specular gloss that is at least 5%lower than the gloss of a film prepared from any one of said polymerconstituents.

DETAILED DESCRIPTION OF THE INVENTION

Polymer compatibility as defined herein is the ability of a mixture oftwo or more polymer constituents to remain dispersed within one anotherwithout causing appreciable scattering of light. Polymer compatibilityis related to the relative proportions of the polymeric constituents ofthe mixture, i.e., a particular combination of polymers may exhibitincompatibility only in certain proportions. Polymer incompatibility isevidenced by the formation of haze in the cast film. The haze can be dueto the formation of polymer domains, which scatter light rather thanspecularly reflect it. As long as the polymer domains are smaller thanthe wavelength of the light passing through the film, no significantimage impairment will result from light scatter. If two or more polymersare only slightly incompatible, a film prepared from a blend or mixtureof such polymers, when applied as a covering to a proof, will lower thegloss of the proof without impairing the clarity of the image. In otherwords, the film will be substantially transparent, with an absence ofperceptible haze, but will exhibit lowered gloss relative to filmsprepared from the pure polymers.

If the polymers are too incompatible the resulting film will be too hazyand when applied to a proof will give an image that is muddy or blurred.Ultimately, if the polymers are grossly incompatible, it may not bepossible to make an integral film from them at all without incurringsuch problems as "orange peel" or other film structure problems.

For purposes of this application, slightly incompatible polymers aredefined as two or more polymers that may be blended in at least someproportions to form a substantially transparent integral film whichexhibits a gloss lower than a film formed for any one, i.e., the onewhich exhibits the lowest gloss, of the component polymers. Preferably,the slightly incompatible polymers must be capable of forming a filmwhich has a gloss at least 5% lower than any one of the componentincompatible polymers. More preferably, the slightly incompatiblepolymers should be capable of forming a film having a gloss at least 10%lower than a film formed from any one of the component incompatiblepolymers. It is frequently possible, however, to utilize the slightlyincompatible polymers of the invention to achieve a very substantiallowering of gloss, e.g. in the range of 75% or more.

In general, it is an object of this invention to provide a topcoat orprotective polymeric covering for image-bearing photosensitive surfaces,including pre-press color proofs, which will exhibit a 20° speculargloss having a predetermined value in the range of about 40 to 80 glossunits, more preferably, 50-70 gloss units, while providing adequateprotection from scratching and marring. It is a further object of thisinvention to provide protective polymeric coverings for image bearingsurfaces having a broad range of lower gloss levels. In some instancesit may be desirable to apply a protective covering having a 20° speculargloss less than 40 gloss units, and sometimes even lower than 25 glossunits.

Slight polymer incompatibility as defined herein is a general phenomenonwhich has been demonstrated with films prepared from mixtures ofpolymers of a number of different chemical compositions. For example,this phenomenon has been demonstrated with films prepared from mixturesof the following polymers:

Ex. (1) a 60/40 ethylene/vinylacetate copolymer of medium molecularweight (inherent viscosity=0.70 measured at 30° C., 0.25 g polymer in100 ml toluene) (Elvax® 40w, E. I. du Pont de Nemours and Company,Wilmington, DE) and a polymethylmethacrylate of high molecular weight(inherent viscosity 1.38 at 20° C., 0.25 g polymer in 50 ml chloroform,No. 50 Cannon-Fenske Viscometer) (Elvacite®2051, E. I. du Pont deNemours and Company, Wilmington, DE):

EX. (2) a 60/40 ethylene/vinylacetate copolymer of medium molecularweight (inherent viscosity=0.70 measured at 30° C., 0.25 g polymer in100 ml toluene) (Elvax® 40w, E. I. du Pont de Nemours and Company,Wilmington, DE); a polymethylmethacrylate of high molecular weight(inherent viscosity 1.38 at 20° C., 0.25 g polymer in 50 ml chloroform,No. 50 Cannon-Fenske Viscometer) (Elvacite®2051, E. I. du Pont deNemours and Company, Wilmington, DE); and a polyvinylacetate of mediummolecular weight (Brookfield viscosity=825 cps at 20° C., 60 rpm, 30%polymer in benzene) (Vinac® B-15, Air Products, Allentown, PA);

EX. (3) a polycarbonate of high molecular weight (melt index=3, ASTMD-1238, Condition O) (Calibre® 300-3, Dow Chemical, Midland, MI) and apolymethylmethacrylate of high molecular weight (inherent viscosity 1.38at 20° C., 0.25 g polymer in 50 ml chloroform, No. 50 Cannon-FenskeViscometer) (Elvacite®2051, E. I. du Pont de Nemours and Company,Wilmington, DE);

EX. (4) a polycarbonate of high molecular weight (melt index=3, ASTMD-1238, Condition O) (Calibre° 300-3, Dow Chemical, Midland, MI) and apolystyrene of high molecular weight (melt index=1.6, ASTM D-1238,Condition G) (Styron® 685D, Dow Chemical, Midland, MI);

EX. (5) a polyamide of high molecular weight (melt index of 5-15 at 347°F.) (Macromelt® 6900, Henkel Corp., Minneapolis, MN) and a polyamide ofhigh molecular weight (viscosity=40-60 poise at 410° (Macromelt® 6238,Henkel Corp., Minneapolis, MN);

EX. (6) a polyamide of high molecular weight (melt index of 5-15 at 347°F.) (Macromelt® 6900, Henkel Corp., Minneapolis, MN) and apolybutylmethacrylate resin (Brookfield viscosity=235-325 cps at 25° C.,40% solution in toluene) (Acryloid® B66 Rohm and Haas, Philadelphia,PA);

EX. (7) a polyester of medium molecular weight (Brookfield viscosity=500cps at 20° C., 30% polymer in toluene) (Vitel® 222, Goodyear Tire andRubber Co., Akron, OH) and a polybutylethacrylate resin (Brookfieldviscosity=235-325 cps at 25° C., 40% solution in toluene) (Acryloid®B66, Rohm and Haas, Philadelphia, PA);

EX. (8) a polyester of medium molecular weight (Brookfield viscosity=500cps at 20° C., 30% polymer in toluene) (Vitel® 222, Goodyear Tire andRubber Co., Akron, OH) and a polystyrene of high molecular weight (meltindex=1.6, ASTM D-1238, Condition G) (Styron® 685D, Dow Chemical,Midland, MI);

EX. (11) a polymethylmethacrylate of high molecular weight (inherentviscosity 1.38 at 20° C., 0.25 g polymer in 50 ml chloroform, No. 50Canon-Fenske Viscometer) (Elvacite®2051, E. I. du Pont de Nemours andCompany, Wilmington, DE); a polyvinylacetate of medium molecular weight(Brookfield viscosity=825 cps at 20° C., 60 rpm, 30% polymer in benzene)(Vinac® B-15, Air Products, Allentown, PA); and a polyethylene glycol oflow molecular weight (minimum Brookfield viscosity=100 cst at 38° C.,25% polymer in water) (Carbowax® 20M, Union Carbide, Danbury, Ct.).

Accordingly, the following are examples of mixtures of slightlyincompatible polymers which can be used to prepare polymeric filmshaving the desired lowering of gloss: (a) an ethylene/vinylacetatecopolymer and polymethylmethacrylate; (b) an ethylene/vinylacetatecopolymer, polymethylmethacrylate, and polyvinylacetate; (c)polycarbonate and polymethylmethacrylate; (d) polycarbonate andpolystyrene; (e) polyamides; (f) polybutylmethacrylate and a polyamide;(g) a polyester and polybutylmethacrylate; (h) a polyester andpolystyrene; (i) polyvinylacetate, polymethylmethacrylate, andpolyethylene glycol.

Preferred is a protective covering wherein the polymeric film consistsessentially of a mixture of at least two slightly incompatible polymersselected from: (a) an ethylene/vinylacetate copolymer andpolymethylmethacrylate; (b) an ethylene/vinylacetate copolymer.

polymethylmethacrylate, and polyvinylacetate; (c) polycarbonate andpolymethylmethacrylate; (d) polycarbonate and polystyrene; and (e)polyvinylacetate, polymethylmethacrylate, and polyethylene glycol.

More preferred mixtures of slightly incompatible polymers are (1) anethylene/polyvinylacetate copolymer, polymethylmethacrylate, andpolyvinylacetate, and (2) polymethylmethacrylate, polyvinylacetate, andpolyethylene glycol.

Specifically preferred is a polymer film which consists essentially ofabout 10-90% polymethylmethacrylate, 10-90% polyvinylacetate, and 2-30%polyethylene glycol.

Particularly preferred is a polymeric film as described in Example 13,which consists essentially of a mixture of slightly incompatiblepolymers which is about 65% polymethylmethacrylate, about 29%polyvinylacetate, and about 4% polyethylene glycol, and which exhibits a20° specular gloss of about 54 gloss units when coated from a methylenechloride/isopropanol solution.

While it is generally not possible to predict in advance whichcombinations of polymers will exhibit the desired slight incompatibilityand in what proportions, it is a relatively simple matter for thoseskilled in the art to follow the teaching set forth herein to determinewhether or not a film prepared from a particular blend of polymers doesor does not exhibit the desired lowering of gloss. By measuring thegloss of films formed from varying proportions of two or more slightlyincompatible polymers, it is possible to choose a film having thedesired degree of lowered gloss. It frequently is possible to prepare asubstantially transparent film having a gloss value much lower than anyof the individual polymer components. This effect of slight polymerincompatibility results in an expanded range of gloss values within asingle system of polymers, and may enable preparation of a protectivefilm having a particular level of gloss, together with the othercharacteristics needed in a protective covering applied to an imagedsurface.

The protective polymeric covering should be thick enough to ensurestructural integrity, but thin enough to avoid distortion of the imagethrough a three-dimensional effect. In general, the coating weight ofthe polymeric layer should be in the range of about 40-200 mg/dm². Thefinal thickness of this layer should not exceed about 0.002 cm, and ispreferably about 0.001 cm thick.

The Wetting Layer

Depending on the nature of the imaged surface on which the protectivecovering is to be used, it is sometimes necessary to add a second,"wetting layer" or adhesive layer, which is disposed between thepolymeric film of the invention and the imaged surface. Such a layer maybe particularly useful when the imaged surface is a tacky compositionwhich has been toned with a colored particulate material. When theprotective polymeric covering is placed directly on a toned image ofthis type, it is sometimes observed that the optical density changeswith time over the course of several hours before reaching itsequilibrium level. It is believed that this may be due to incompletewetting of the toned surface. When a "wetting layer" is used with theprotective polymeric covering, the equilibrium optical density isachieved immediately after lamination. Of course, even when the imagedsurface to be protected by the polymeric film does not require a"wetting layer" per se, it may be necessary or desirable to use anadhesive layer to improve adhesion.

The wetting or adhesive layer may be chosen from a great number ofmaterials that will wet or flow into the toned areas. Preferably, thislayer will be of a clear, nonphotosensitive, tacky or slightly softdeformable organic material. Particularly preferred materials areelastomeric polymers and mixtures thereof. Rubber type polymers, bothnatural and synthetic, may be used, e.g., polyisobutylene, Thiokol A,nitrile rubbers, butyl rubber, chlorinated rubbers, polymers ofbutadiene, poly(vinylisobutylether), polyisoprene, and random, teleblockand block copolymers of butadiene or isoprene copolymerized withstyrene, and neoprene, silicone elastomers, etc., in variousproportions. Additionally, any highly plasticized thermoplasticpolymeric film will function as a wetting layer. As is readily apparentto those skilled in the art, the wetting layer may also contain suchingredients as tackifiers, anti-oxidants, etc. Any suitable solvent maybe used to coat the wetting layer. The coating weight of the wettinglayer may be varied over a wide range and is primarily determined by theother physical property requirements of the system. That is, the minimumcoating weight is that which will provide a film with sufficientthickness to laminate evenly over the imaged surface. The maximumcoating weight is that which will provide a film which will not distortthe image, i.e., give a three-dimensional appearance. In general, thewetting layer should have a coating weight in the range of 10-100mg/dm², and preferably 50 mg/dm². As noted above, the coating weight ofthe protective polymeric layer alone should be in the range of about40-200 mg/dm², and the thickness of this layer should not exceed 0.002cm, preferably about 0.001 cm. Accordingly, the thickness of the wettinglayer should be such that the total thickness of the finishedcoversheet, i.e., protective polymeric covering and wetting layercombined, does not exceed about 0.002 cm.

As will be readily apparent to those skilled in the art, the protectivecovering of the invention may have additional layers adjacent to theprotective polymeric layer and adjacent to the wetting layer tofacilitate handling and storage. Such additional layers may beparticularly useful if the protective covering is to be stored in a rollprior to use. The covering on the wetting layer would be removed priorto lamination to the imaged surface; the covering on the protectivepolymeric film layer would preferably be removed after lamination.Suitable materials for these additional coverings would includesilicone-treated polyester, polyethylene, etc., which release readilyfrom the layer they serve to protect.

The phase "consisting essentially of" is intended to the presentdisclosure to have its customary meaning, namely, that the films of theinvention are limited to the specified ingredients and other ingredientsthat do not materially affect the basic and novel characteristics of thecompositions claimed. For example, while it is understood that thepolymer films must contain at least two slightly incompatible polymers,other compatible or slightly incompatible polymers may also be presentwhen needed to achieve a film having a particular set of properties. Itis also understood that the compositions may include a variety ofadditives, such as optical brighteners, anti-oxidants, coating aids, UVlight attenuators, etc. In other words, unspecified materials are notexcluded so long as they do not prevent the benefits of the inventionfrom being realized.

Furthermore, as is well known to those skilled in the art, commerciallyavailable polymers of the type described herein may contain smallamounts of other polymerized material. It is intended that the chemicaldescriptions given are interpreted to mean those polymers that aresubstantially made up of the monomer(s) indicated. For example, acommercial polymethylmethacrylate will frequently contain a few percentof ethylmethacrylate. It is comtemplated that such copolymers will fallwithin the invention as disclosed.

EXAMPLES

The following examples illustrate some combinations of slightlyincompatible polymers which can be utilized to prepare integral filmshaving various degrees of lowered gloss, which may be useful as aprotective covering or coversheet for pre-press color proofs,photographs, or other imaged surfaces. These examples demonstrate howthe amount of gloss can be varied by blending various polymers indifferent proportions. It can be seen that blends of slightlyincompatible polymers provide an expanded range of gloss levels within aparticular system of polymers. Other combinations of slightlyincompatible polymers useful for preparing optically clear integralfilms having a desirable range of reduced gloss values can be determinedby measuring the specular gloss of easily prepared test films.

Gloss measurements are made using a Gardner Glossgard Digital Modelglossmeter (Gardner Co., Bethesda, MD) at a 20° angle of incidence.Before actual measurements are taken on the samples, care was taken toinsure proper calibration of the glossmeter at each of the angles byreading and adjusting (as necessary) the values obtained for white andblack tile standards provided by the manufacturer. The range of theGlossgard glossmeter is 0.0-199.9 gloss units with a precision of +/-0.5gloss units. Once the instrument has been calibrated, successive glossmeasurements within a series may be compared. The gloss of a sample wasmeasured by placing the glossmeter's aperture in the middle of thesample and recording the gloss value taken at a 20° angle of incidence.Care was also taken to insure that the direction of measurements on thesamples relative to the aperture was the same for all samples and inparticular, within the polymeric series being evaluated. All laminationswere performed at 210-250° F. on a Cromalin® laminator, manufactured byE. I. du Pont de Nemours and Company, Wilmington, DE. Unless otherwisespecified, all gloss values are in gloss units and all quantities are ingrams.

Examples 1-9

The polymer films were prepared by dissolving the named polymers in thevarying proportions listed for each example in the organic solvent ormixture of solvents indicated to form a 15% w/w solution. Theingredients were thoroughly mixed and coated onto a 0.00254 cm thicksilicone-treated transparent polyethylene terephthalate support using a0.005 cm doctor blade. After drying, the resulting film had a thicknessof 0.0008 cm. The polymeric films of the invention are prepared bycoating from an essentially organic solvent system. This solvent systemis a single organic solvent or mixture of organic solvents suitable fordissolving the particular mixture of slightly incompatible polymers. Ascan be seen by comparing Examples 1 and 9, the choice of organic solventsystem may affect the gloss of the resulting film.

Examples 1-13 were carried out with a negative-working photosensitiveelement similar to that described in Cohen and Fan, U.S. Pat. No.4,174,216, the teaching of which is incorporated by reference. Thisnegative-working element comprises, in order from top to bottom, (1) astrippable cover sheet, (2) a photoadherent layer comprising a materialwith ethylenically unsaturated or benzophenone type groups, which isgenerally nontacky, (3) a tonable organic contiguous layer, i.e., atacky, nonphotosensitive elastomeric layer which is tonable byapplication of particulate material, and (4) a sheet support. Thesamples were prepared by laminating the above element (after removal ofthe sheet support) to a support comprising polyethylene-coated paper,and removing the strippable polyester coversheet. The polymeric testfilm on silicone-treated polyester was then laminated to the surface ofthe element such that the polymer film was in surface-to-surface contactwith the photoadherent layer. The silicone-treated polyester support wasthen removed, and the gloss measurements were carried out as describedabove.

Example 14 utilizes a layer of positive Cromalin® (E. I. du Pont deNemours and Company, Wilmington, DE), similar to the positive-workingphotopolymerizable element described in U.S. Pat. No. 3,649,268, Examplenumber 3.

Example 1

    __________________________________________________________________________    A        B   C  D   E  F   G  H   I                                           __________________________________________________________________________    Methylene                                                                           170                                                                              170 170                                                                              170 170                                                                              170 170                                                                              170 170                                         Chloride                                                                      E/PVAc.sup.(1)                                                                      0  3   6  9   12 15  18 24  30                                          PMMA.sup.(1)                                                                        30 27  24 21  18 15  12 6   0                                           % E/PVAc                                                                            0  10  20 30  40 50  60 80  100                                         % PMMA                                                                              100                                                                              90  80 70  60 50  40 20  0                                           GLOSS 20°                                                                    42.0                                                                             39.8                                                                              18.7                                                                             14.8                                                                              9.7                                                                              12.3                                                                              14.7                                                                             39.3                                                                              46.0                                        __________________________________________________________________________     .sup.(1) E/PVAc = 60/40 ethylene/vinylacetate copolymer, inherent             viscosity = 0.70 measured at 30° C., 0.25 g polymer in 100 ml          toluene, Elvax ® 40w, E. I. du Pont de Nemours and Company,               Wilmington, DE. PMMA = polymethylmethacrylate inherent viscosity = 1.38 a     20° C., 0.25 g of polymer in 50 ml chloroform, No. 50 CannonFenske     Viscometer, Elvacite ® 2051, E. I. du Pont de Nemours and Company,        Wilmington, DE.                                                          

Example 2

    __________________________________________________________________________    A        B   C  D   E  F   G  H   I                                           __________________________________________________________________________    Methylene                                                                           170                                                                              170 170                                                                              170 170                                                                              170 170                                                                              170 170                                         Chloride                                                                      E/PVAc.sup.(1)                                                                      0  3   7.5                                                                              12  15 18  21 24  27                                          PMMA.sup.(1)                                                                        30 13.5                                                                              11.3                                                                             9   7.5                                                                              6   4.5                                                                              3   1.5                                         PVAc.sup.(2)                                                                        0  13.5                                                                              11.3                                                                             9   7.5                                                                              6   4.5                                                                              3   1.5                                         % E/PVAc                                                                            0  10  25 40  50 60  70 80  90                                          % PMMA                                                                              100                                                                              45  37.5                                                                             30  25 20  15 10  5                                           % PVAc                                                                              0  45  37.5                                                                             30  25 20  15 10  5                                           GLOSS 20°                                                                    42.0                                                                             45.3                                                                              31.3                                                                             20.7                                                                              14.4                                                                             27.4                                                                              28.3                                                                             38.9                                                                              46.5                                        __________________________________________________________________________     .sup.(2) PVAc = polyvinylacetate, Brookfield viscosity = 825 cps at           20° C., 60 RPM, 30% polymer in benzene, Vinac ® B15, Air           Products Corp., Allentown, PA.                                           

Example 3

    ______________________________________                                               A     B       C       D     E     F                                    ______________________________________                                        Methylene                                                                              170     170     170   170   170   170                                Chloride                                                                      PC.sup.(3)                                                                             30      24      18    12    6     0                                  PMMA.sup.(1)                                                                           0       6       12    18    24    30                                 % PC     100     80      60    40    20    0                                  % PMMA   0       20      40    60    80    100                                GLOSS 20°                                                                       64.6    58.0    43.3  47.6  48.3  50.0                               ______________________________________                                         .sup.(3) PC = polycarbonate, melt index = 3 (ASTM D1238, Condition O),        Calibre ® 3003, Dow Chemical, Midland, MI.                           

Example 4

    ______________________________________                                        A            B      C      D    E    F    G                                   ______________________________________                                        Methylene                                                                             170      170    170  170  170  170  170                               Chloride                                                                      PC.sup.(3)                                                                             30      24     18   15   12    6    0                                S.sup.(4)                                                                              0        6     12   15   18   24    30                               % PC    100      80     60   50   40   20    0                                % S      0       20     40   50   60   80   100                               GLOSS 20°                                                                      64.6     67.2   64.0 63.5 60.7 63.5 68.7                              ______________________________________                                         .sup.(4) S = polystyrene, melt index = 1.6 (ASTM D1238, Condition G),         Styron ® 685D, Dow Chemical, Midland. MI.                            

Example 5

    ______________________________________                                                     A    B      C      D    E    F                                   ______________________________________                                        Methylene Chloride                                                                           157    157    157  157  157  157                               Methanol       13     13     13   13   13   13                                Macromelt ® 6900.sup.(5)                                                                 30     24     18   12    6    0                                Macromelt ® 6238.sup.(5)                                                                  0      6     12   18   24   30                                % Macromelt ® 6900.sup.(5)                                                               100    80     60   40   20    0                                % Macromelt ® 6238.sup.(5)                                                                0     20     40   60   80   100                               GLOSS 20°                                                                             46.0   46.2   38.6 19.6 27.3 43.7                              ______________________________________                                         .sup.(5) Macromelt ® is a registered trademark for polyamide resins       made by the Henkel Corp., Minneapolis, MN.                               

Example 6

    ______________________________________                                                  A    B      C      D    E    F    G                                 ______________________________________                                        Methylene   157    157    157  157  157  157  157                             Chloride                                                                      Methanol    13     13     13   13   13   13   13                              Macromelt ® 6900.sup.(5)                                                              30      6     12   15   18   24    0                              PBMA.sup.(6)                                                                               0     24     18   15   12    6   30                              % Macromelt ®                                                                         100    20     40   50   60   80    0                              6900                                                                          % PBMA       0     80     60   50   40   20   100                             GLOSS 20°                                                                          46.0   34.7   25.2 26.0 21.7 47.0 47.5                            ______________________________________                                         .sup.(6) PBMA = polybutylmethacrylate, Brookfield Viscosity = 235-325 cps     at 25° C., 40% solution in toluene, Acryloid ® B66, Rohm and       Haas, Philadelphia, PA.                                                  

Example 7

    ______________________________________                                                    A    B      C      D    E    F                                    ______________________________________                                        Methylene Chloride                                                                          170    170    170  170  170  170                                Vitel ® 222.sup.(7)                                                                     30     24     18   12    6    0                                 PBMA.sup.(6)   0      6     12   18   24   30                                 % Vitel ® 222                                                                           100    80     60   40   20    0                                 % PBMA         0     20     40   60   80   100                                GLOSS 20°                                                                            65.4   4.97   49.3 39.8 49.3 45.0                               ______________________________________                                         .sup.(7) Vitel ® is a registered trademark for a polyester (Brookfiel     viscosity = 500 cps at 20° C., 30% polymer in toluene) made by the     Goodyear Tire & Rubber Co., Akron, OH.                                   

Example 8

    ______________________________________                                                A    B      C      D     E    F    G                                  ______________________________________                                        Methylene 170    170    170  170   170  170  170                              Chloride                                                                      Vitel ® 222.sup.(7)                                                                  0      6     12   15    18   24   30                               S.sup.(4) 30     24     18   15/ 12                                                                               6    0                                    % Vitel ® 222                                                                        0     20 40  50   60    80   100                                   % S       100    80     60   50    40   20    0                               GLOSS 20°                                                                        71.2   54.4   52.1 49.8  36.1 48.1 65.4                             ______________________________________                                    

Example 9

    ______________________________________                                                  A    B       C      D     E    F                                    ______________________________________                                        Toluene     170    170     170  170   170  170                                E/PVAc.sup.(1)                                                                            30      6      12   18    24    0                                 PMMA.sup.(1)                                                                               0     24      18   12     6   30                                 % E/PVAc    100    20      40   60    80    0                                 % PMMA       0     80      60   40    20   100                                GLOSS 20°                                                                          37.7   33.6    10.4 25.0  39.2 49.0                               ______________________________________                                    

Comparing Examples 1 and 9 demonstrates that the organic solvent fromwhich a mixture of slightly incompatible polymers is coated can affectthe gloss of the resulting film, but that the gloss lowering effectwhich characterizes such polymer mixtures occurs with different organicsolvents or mixtures of solvents.

Example 10

The following example demonstrates that two polymers which are verycompatible with one another can be blended without any significantlowering of the gloss of the resulting film. In this case, bothpolyvinylacetate and polymethylmethacrylate films exhibit similar glossvalues, and the films prepared from these two polymers blended invarious proportions did not show the characteristic decrease in glossassociated with slight polymer incompatibility.

    ______________________________________                                                    A    B      C      D    E    F                                    ______________________________________                                        Methylene Chloride                                                                          170    170    170  170  170  170                                PMMA.sup.(1)  30     24     18   12    6    0                                 PVAc.sup.(2)   0      6     12   18   24   30                                 % PMMA        100    80     60   40   20    0                                 % PVAc         0     20     40   60   80   100                                GLOSS 20°                                                                            43.1   45.6 46.5                                                                            46.6 46.7 43.3                                    ______________________________________                                    

Example 11

The following example demonstrates that a small amount of a slightlyincompatible polymer can significantly lower the gloss of the resultingfilm. In this case polyethylene glycol is added to lower the gloss ofthe mixture of polymethylmethacrylate and polyvinylacetate in Example10. Polyethylene oxide appears to have no effect.

    ______________________________________                                                   A     B       C       D     E                                      ______________________________________                                        Methylene Chloride                                                                         170     170     170   170   170                                  PMMA.sup.(1) 30      19.7    20.4  19.6   0                                   PVAc.sup.(2)  0       9.1     9.4   9.0  30                                   PEG.sup.(8)   0       1.2     0     1.2   0                                   PEO.sup.(8)   0       0       0.7   0.7   0                                   % PMMA       100     65.7    68.0  65.3   0                                   % PVAc        0      30.3    31.3  30.0  100                                  % PEG         0       4.0     0     4.0   0                                   % PEO         0       0       0.7   0.7   0                                   GLOSS 20°                                                                           55.5    49.0    52.0  49.1  52.6                                 ______________________________________                                         .sup.(8) PEG = polyethylene glycol, minimum Brookfield viscosity = 100 cs     at 38° C., 25% polymer in water, Carbowax ® 20M, Union Carbide     Danbury, Ct. PEO = polyethylene oxide, MW = 300,000 (weighted average),       Polyox ® WSRN 3000, Union Carbide, Danbury, Ct.                      

Example 12

To a solution of 82.0 vol. % methylene chloride and 18.0 vol. %ispropanol were added the following ingredients in the amountsindicated:

    ______________________________________                                        Ingredient      Amount (% of Solids)                                          ______________________________________                                        PMMA.sup.(1)    35.0                                                          PVAc.sup.(2)    59.4                                                          PEG.sup.(8)     4.0                                                           Optical brightener.sup.(9)                                                                    0.5                                                           UV stabilizer.sup.(9)                                                                         0.5                                                           Polyethylene oxide.sup.(8)                                                                    0.5                                                           Anti-oxidant.sup.(9)                                                                          0.1                                                           ______________________________________                                         .sup.(9) optical brightener =                                                 7(4'-chloro-6-diethyl-amino-1',3',5'-triazine-4-'yl)-amino-3-phenyl-couma    in UV stabilizer =                                                             2[2'-hydroxy-3',5'-bis-(1",1"-dimethylpropane)phenyl]-benzotriazole           antioxidant = tetra                                                           bis[methylene3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate methane    

The above solution was cast into a film and laminated onto negativeCromalin® as in the previous examples. The gloss measured at 20° was59.3.

Example 13

This example illustrates the use of a two-layer cover film. Thefollowing ingredients were added to a methylene chloride/isopropanol(82/18 vol/vol) solution in the amounts given:

    ______________________________________                                        Ingredient      Amount (% of Solids)                                          ______________________________________                                        PMMA.sup.(1)    65.0                                                          PVAc.sup.(2)    29.4                                                          PEG.sup.(8)     4.0                                                           Optical brightener.sup.(9)                                                                    0.5                                                           UV stabilizer.sup.(9)                                                                         0.5                                                           PEO.sup.(8)     0.5                                                           Anti-oxidant.sup.(9)                                                                          0.1                                                           ______________________________________                                    

This was coated onto a 0.00254 cm thick transparent polyethyleneterephthalate support using a 0.0050 cm doctor blade. A second solutionwas made in methylene chloride of the following ingredients:

    ______________________________________                                        Ingredient          Amount (% of Solids)                                      ______________________________________                                        Polybutadiene, ML-4 (Mooney                                                                       90.49                                                     Viscosity = 55), Diene ® 55AC,                                            Goodyear, Akron, OH                                                           Styrene/butadiene (23/77),                                                                        9.26                                                      ML-4 (Mooney Viscosity = 26),                                                 Gentro ® 1506, Gencorp.                                                   Anti-oxidant.sup.(9)                                                                              0.25                                                      ______________________________________                                    

This solution was coated onto a 0.00254 cm thick silicone treatedpolyethylene terephthalate support using a 0.0050 cm doctor blade. Thesecond film was then laminated to the first film at ambient temperaturessuch that the two polymeric layers were in contact. The silicone treatedpolyester support layer was removed and the composite film laminated toa Cromalin® film as in Example 10. The polyester coversheet was removedand the gloss measurements were made. The gloss of the PMMA, PVAc, PEGfilm at 20° was 54.0

Example 14

This example illustrates the use of the polymeric films with multicolorsurprint proofs.

A four-color proof was made in the following manner:

(1) a layer of positive Cromalin® (E. I. du Pont de Nemours and Company,Wilmington, DE) was laminated to a plastic coated paper receptor at 250°F;

(2) it was exposed with ultraviolet light under vacuum with a positiveseparation (yellow) on top of the film for 10 sec. with a 5 Kw light;

(3) the polyester coversheet was removed and a yellow colored film on apolyester support as described in German application P 36 25 014.7 waslaminated to the exposed film;

(4) the polyester support containing the yellow colored film was peeledoff the receptor leaving behind a positive yellow image;

(5) steps 1-4 were repeated sequentially using positive magenta, cyan,and black separations and magenta, cyan, and black colored films toobtain a four-color surprint proof.

In Example 14-A, the polymeric film of Example 12 was laminated to thefour-color proof, and the polyester cover sheet removed. In example14-B, the dual layer polymeric film of Example 13 was laminated to thefour-color proof and the polyester coversheet removed. The glossmeasurements were made as above and the results were summarized below.If negative Cromalin® were used as a coversheet (given an overallexposure and the polyester coversheet left on) the resulting gloss wouldbe expected to be about 107. If positive Cromalin® were used as acoversheet (given an overall exposure and the polyester coversheetremoved) the resulting gloss would be expected to be about 59.

    ______________________________________                                                        14-A 14-B                                                     ______________________________________                                        GLOSS 20°  52.7   50.7                                                 ______________________________________                                    

I claim:
 1. A method of providing a pre-press color proof with alower-gloss protective covering, comprising in the stated order thesteps of:(a) providing an element which comprises a thin, substantiallytransparent, nonphotosensitive, integral polymeric film having athickness not greater than 0.002 cm on a removable substrate, saidpolymeric film consisting essentially of a mixture of at least twoslightly incompatible polymers, said mixture of slightly incompatiblepolymers having been dissolved in an essentially organic solvent system,coated on the substrate, and dried, so that said polymeric film exhibitsa 20° specular gloss that is at least 5% lower than a film prepared inthe same manner from any one of said polymer constituents; (b)laminating the element to the surface of the prepress color proof, and,(c) removing the removable substrate, whereby the polymeric film becomesthe outermost layer of the pre-press color proof.
 2. A method accordingto claim 1, wherein the polymeric film has a thickness not greater than0.001 cm.
 3. A method according to claim 1, wherein the polymeric filmhas a 20° specular gloss that is at least 10% lower than a film preparedfrom any one of said polymer constituents.
 4. A method according toclaim 1, wherein the element which is provided comprises, in the statedorder, a wetting layer, said polymeric film, and said removablesubstrate, and wherein the element is laminated to the pre-press colorproof with the wetting layer in surface-to-surface contact with thepre-press color proof.
 5. A method according to claim 4, wherein thewetting layer comprises an elastomeric polymer.
 6. A method according toclaim 4, wherein the pre-press color proof is toned with a particulatematerial.
 7. A method according to claim 5, wherein the pre-press colorproof is toned with a particulate material.
 8. A method according toclaim 1, wherein the polymeric film consists essentially of a mixture ofat least two sightly incompatible polymers selected from the groupconsisting of:(a) an ethylene/vinylacetate copolymer andpolymethylmethacrylate; (b) an ethylene/vinylacetate copolymer,polymethylmethacrylate, and polyvinylacetate; (c) polycarbonate andpolymethylmethacrylate; (d) polycarbonate and polystyrene; (e) twodifferent polyamides; (f) polybutylmethacrylate and a polyamide; (g) apolyester and polybutylmethacrylate; (h) a polyester and polystyrene;(i) polyvinylacetate, polymethylmethacrylate, and polyethylene glycol.9. A method according to claim 1, wherein the polymeric film consistsessentially of a mixture of at least two slightly incompatible polymersselected from the group consisting of:(a) an ethylene/vinylacetatecopolymer and polymethylmethacrylate; (b) an ethylene/vinylacetatecopolymer, polymethylmethacrylate, and polyvinylacetate; (c)polycarbonate and polymethylmethacrylate; (d) polycarbonate andpolystyrene; and (e) polyvinylacetate, polymethylmethacrylate, andpolyethylene glycol.
 10. A method according to claim 9, wherein thepolymeric film consists essentially of a mixture of at least twoslightly incompatible polymers selected from the group consisting of:(a)an ethylene/vinylacetate copolymer, polymethylmethacrylate, andpolyvinylacetate, and (b) polymethylmethacrylate, polyvinylacetate, andpolyethylene glycol.
 11. A method according to claim 10, wherein thepolymeric film consists essentially of a mixture ofpolymethylmethacrylate, polyvinylacetate, and polyethylene glycol.
 12. Amethod according to claim 11, wherein the polymeric film consistsessentially of a mixture of about 10-90% polymethylmethacrylate, 10-90%polyvinylacetate, and 2-30% polyethylene glycol.
 13. A method accordingto claim 12, wherein the polymeric film consists essentially of amixture of about 65% polymethylmethacrylate, 29% polyvinylacetate, andabout 4% polyethylene glycol.
 14. A method according to claim 4, whereinthe polymeric film consists essentially of a mixture of about 10-90%polymethylmethacrylate, 10-90% polyvinylacetate, and 2-30% polyethyleneglycol.
 15. A method according to claim 14, wherein the wetting layercomprises an elastomeric polymer.
 16. A method according to claim 15,wherein the wetting layer comprises a mixture of 5-95% polybutadiene and5-95% of a styrene/butadiene copolymer.
 17. A method according to claim14, wherein the polymeric film consists essentially of a mixture ofabout 65% polymethylmethacrylate, 29% polyvinylacetate, and about 4%polyethylene glycol and wherein the wetting layer comprises a mixture ofabout 90% polybutadiene and about 9% of a styrene/butadiene copolymer.18. A method according to claim 4, wherein the polymeric film consistsessentially of a mixture of at least two slightly incompatible polymersselected from the group consisting of:(a) an ethylene/vinylacetatecopolymer and polymethylmethacrylate; (b) an ethylene/vinylacetatecopolymer, polymethylmethacrylate, and polyvinylacetate; (c)polycarbonate and polymethylmethacrylate; (d) polycarbonate andpolystyrene; (e) two different polyamides; (f) polybutylmethacrylate anda polyamide; (g) a polyester and polybutylmethacrylate; (h) a polyesterand polystyrene; (i) polyvinylacetate, polymethylmethacrylate, andpolyethylene glycol.
 19. A method according to claim 18, wherein thepolymeric film consists essentially of a mixture of at least twoslightly incompatible polymers selected from the group consisting of:(a)an ethylene/vinylacetate copolymer and polymethylmethacrylate; (b) anethylene/vinylacetate copolymer, polymethylmethacrylate, andpolyvinylacetate; (c) polycarbonate and polymethylmethacrylate; (d)polycarbonate and polystyrene; and (e) polyvinylacetate,polymethylmethacrylate, and polyethylene glycol.
 20. A method accordingto claim 19, wherein the polymeric film consists essentially of amixture of at least two slightly incompatible polymers selected from thegroup consisting of:(a) an ethylene/vinylacetate copolymer,polymethylmethacrylate, and polyvinylacetate, and (b)polymethylmethacrylate, polyvinylacetate, and polyethylene glycol.
 21. Amethod according to claim 20, wherein the polymeric film consistsessentially of a mixture of polymethylmethacrylate, polyvinylacetate,and polyethylene glycol.
 22. A method according to claim 21, wherein thepolymeric film consists essentially of about 10-90%polymethylmethacrylate, 10-90% polyvinylacetate, and 2-30% polyethyleneglycol.
 23. A method according to claim 22, wherein the polymeric filmconsists essentially of a mixture of about 65% polymethylmethacrylate,about 29% polyvinylacetate, and about 4% polyethylene glycol.
 24. Amethod according to claim 18, wherein the wetting layer comprises anelastomeric polymer.
 25. A method according to claim 20, wherein thewetting layer comprises an elastomeric polymer.
 26. A method accordingto claim 25 wherein the wetting layer comprises a mixture of 5-95%polybutadiene and 5-95% of a styrene/butadiene copolymer.
 27. A methodaccording to claim 26, wherein the wetting layer comprises a mixture ofabout 90% polybutadiene and about 9% of a styrene/butadiene copolymer,and wherein the polymeric film consists essentially of a mixture ofabout 65% polymethylmethacrylate, 29% polyvinylacetate, and about 4%polyethylene glycol.
 28. A method according to claim 18, wherein thepre-press color proof is toned with a particulate material.
 29. A methodaccording to claim 24, wherein the pre-press color proof is toned with aparticulate material.
 30. A method of providing a pre-press color proofwith a lower-gloss protective covering, comprising in the stated orderthe steps of:(a) preparing an element comprising a thin, substantiallytransparent, nonphotosensitive, integral polymeric film having athickness not greater than 0.002 cm on a removable substrate, comprisingthe steps of:(i) dissolving at least two slightly incompatible polymersin an essentially organic solvent system, (ii) coating this polymersolution on an appropriate substrate, and (iii) drying, so that thethus-formed polymeric film exhibits a 20° specular gloss that is atleast 5% lower than a film prepared in the same manner from any one ofsaid polymer constituents; (b) laminating the element prepared in step(a) to the surface of the pre-press color proof; and, (c) removing theremovable substrate, whereby the polymeric film becomes the outermostlayer of the pre-press color proof.
 31. A method according to claim 30,wherein the polymeric film has a thickness not greater than 0.001 cm.32. A method according to claim 30, wherein the polymeric film exhibitsa 20° specular gloss that is at least 10% lower than a film prepared inthe same manner from any one of said polymer constituents.
 33. A methodaccording to claim 30, wherein the polymeric film consists essentiallyof a mixture of at least two slightly incompatible polymers selectedfrom the group consisting of:(a) an ethylene/vinylacetate copolymer andpolymethylmethacrylate; (b) an ethylene/vinylacetate copolymer,polymethylmethacrylate, and polyvinylacetate; (c) polycarbonate andpolymethylmethacrylate; (d) polycarbonate and polystyrene; (e) twodifferent polyamides; (f) polybutylmethacrylate and a polyamide; (g) apolyester and polybutylmethacrylate; (h) a polyester and polystyrene;(i) polyvinylacetate, polymethylmethacrylate, and polyethylene glycol.34. A method according to claim 33, wherein the polymeric film consistsessentially of a mixture of at least two slightly incompatible polymersselected from the group consisting of:(a) an ethylene/vinylacetatecopolymer, polymethylmethacrylate, and polyvinylacetate, and (b)polymethylmethacrylate, polyvinylacetate, and polyethylene glycol.
 35. Amethod according to claim 34, wherein the polymeric film consistsessentially of a mixture of polymethylmethacrylate, polyvinylacetate,and polyethylene glycol.
 36. A method according to claim 35, wherein thepolymeric film consists essentially of a mixture of about 10-90%polymethylmethacrylate, 10-90% polyvinylacetate, and 2-30% polyethyleneglycol.
 37. A method according to claim 30, wherein the element preparedin step (a) comprises, in the stated order, a wetting layer, saidpolymeric film, and said removable substrate, and wherein the element islaminated to the pre-press color proof with the wetting layer insurface-to-surface contact with the pre-press color proof.
 38. A methodaccording to claim 37, wherein the pre-press color proof is toned with aparticulate toner.
 39. A method according to claim 37, wherein thewetting layer comprises an elastomeric polymer.
 40. A method accordingto claim 39, wherein the pre-press color proof is toned with aparticulate toner.
 41. A method according to claim 37, wherein thepolymeric film consists essentially of a mixture of at least twoslightly incompatible polymers selected from the group consisting of:(a)an ethylene/vinylacetate copolymer and polymethylmethacrylate; (b) anethylene/vinylacetate copolymer, polymethylmethacrylate, andpolyvinylacetate; (c) polycarbonate and polymethylmethacrylate; (d)polycarbonate and polystyrene; (e) two different polyamides; (f)polybutylmethacrylate and a polyamide; (g) a polyester andpolybutylmethacrylate; (h) a polyester and polystyrene; (i)polyvinylacetate, polymethylmethacrylate, and polyethylene glycol.
 42. Amethod according to claim 41, wherein the polymeric film consistsessentially of a mixture of at least two slightly incompatible polymersselected from the group consisting of:(a) an ethylene/vinylacetatecopolymer, polymethylmethacrylate, and polyvinylacetate, and (b)polymethylmethacrylate, polyvinylacetate, and polyethylene glycol.
 43. Amethod according to claim 42, wherein the polymeric film consistsessentially of a mixture of polymethylmethacrylate, polyvinylacetate,and polyethylene glycol, and the wetting layer comprises a mixture ofpolybutadiene and a styrene/butadiene copolymer.